I've just about finished my ls6/t56 swap and I've got a bad electrical problem. The car runs and idles prefect until the alt is connected as soon as it is connected the car starts missing and dies? I have also made it a one wire system to try and eliminate the problem because it was having the same problem before I made it a one wire alternator with no luck fixing it. The alternator is good and has been tested multiple times and and like I said made into a 1 wire system to avoid the computer. It puts out 14v but as soon as it's connected to the positive battery terminal the car dies then won't start. I'm at a loss? Any insight would be amazing you can reply on here or call me at 2564663617 thanks mitchell

 

Tell us exactly how you have the alternator wired and where the wires are routed on the car.

 

At first I had it ran the original way from the small power block next to the battery. The same way the original alternator was wired. Then I wired it strait from the positive terminal off the alternator to the battery. Both ways there were no changes.

 

You didn't tell us exactly how it is wired. Try again, but this time with all the details for all the connections.

 

I have my pink hots wired to the ignition hot and the main grounds to the back of the block driver side and the Orange constant hot to the battery positive. And like I said the alternator had only the positive post to wire to the battery. I acts like its getting a extra positive signal to the computer that it doesn't like but idk how that's possible

 

Anyone have any ideas?

 

Unplug the alt and see what kind of voltage you're getting on the B terminal. You want 10v or less when running

The alt output lug needs to be connected to the battery circuit somehow. Power dist block, starter lug, or direct to the battery, it doesnt matter

If the engine runs great on 11-12v battery power, but goes wonky when the system rises to its usual 14.4v, then you've got bigger problems

 

I had 7 on the volt meter when I had the alternator ran through the computer but it was doing the same thing before I made it a one wire as it is now. Yesterday I ran everything strait to the battery to avoid any bad connections that might have been in the factory/body harness wiring. I hooked up my alternator after the car was running and and it did the exact same thing not where it would just die or no a start with it hooked up before it was starting . So I feel like I have either a bad computer or my engine harness is pinned wrong. Does that sound like a problem in the computer to you?

 

The engine harness was the only harness that was connected so it has to be the engine harness or computer. Does that sound like a symptom of a bad computer? Like I said the car runs fine until the extra voltage hits the computer.

 

Your subject says ls1, but your thread says ls6? What ECM are you using? My LS6 on the V is using a 12586243 computer, which uses a two wire alt were both run to the ECM --
gray alt -> G75
orange alt -> G15

See these two threads:
http://www.cadillacforums.com/forums...g-problem.html
http://ls1tech.com/forums/generation...lternator.html

 

Do you have another alternator to try? I have seen a couple of alt. have electrical noise and screw with the ecm.

 

Where is the harness from, where is the block from, where is the FEAD from, what ECM - is is a complete drop out from somewhere?

Stock alternators that came from the factory with our cars are quite different than the ones that were implemented in LS cars.

My TPI FEAD alternator had three wires and a battery cable, whereas, my LS1 alternator has a battery cable and one wire from the PCM. Before the engine computer didnt control the alternator, with an LS1 it does.

 

What did you wire to the 4 pin connector at the alternator?

 

09354896 is the computer it's a 04 ctsv ls6 with the stripped fbody harness and 98 accessories and fbody t56. I was using the One wire connector for the alternator harness plugged to the B harness port that you can buy off ebay

 

Also I bought a new alternator and tried it with the same result the only thing I can come up with is the computer is pinned wrong or the computer is bad. Does anyone have the pinning harness for this computer?

 

Is the harness from a '98 too? Those are different than other years.

I don't know what is a "B harness port off ebay". The alternator has a P, L, F, and S terminal in the connector. How do you have that wired?

 

New alternators do not have the same terminal identification as old alts. The jobs are the same, only the connectors follow a more standard A,B,C,D identification. For LS1 alts, B is the exciter and is computer controlled

 

The B was the exciter and it was hooked up to begin with until I made the alternator a one wire system to avoid using the computer because I thought that was the problem. I also tried another brand new alternator with it wired up the same way with the same result. I'm not sure the year of the harness because it was a craigslist buy a couple years ago when I was gathering parts.